This invention relates to an elongated, hollow, thin wall, rigid drive shaft having a flange formed on one end and a coupling configuration, such as spline teeth, formed on its opposite end. The shaft is useful for coupling together a driving and a driven member, such as the differential of an automotive vehicle and a driven wheel.
Drive shafts, particularly for automotive vehicles, are typically formed of solid metal shafts with their opposite ends formed for connecting to the drive and driven members of the vehicle. For example, a flange may be machined on one end of the shaft and the opposite end of the shaft may be provided with external or internal spline-like teeth so that the shaft may be connected to the differential and to a wheel of the vehicle. Because such drive shafts must transmit considerable torque and are subjected to rapid starts and stops of power transmission, they must be rigid and strong enough to perform under both normal and high overload conditions. Thus, drive shafts are made relatively heavy in order to provide the needed rigidity and strength.
It would be desirable to provide, particularly for automotive vehicle use, a lightweight drive shaft, which nevertheless provides the same rigidity and torque carrying capacity as a solid heavy shaft. This is in accordance with the desire to reduce the weight of automotive vehicles as much as possible so as to reduce vehicle fuel consumption and unslung weight.
One method of reducing a hollow, lightweight shaft is described, in general, in my prior patents which relate to the extrusion of ring-like metal blanks through tubular die throats. The blanks are pushed through the die throats by a suitable punch having an extension which forms a mandrel-like member within the tubular die and blank. In general, this method may be used to produce hollow, thin wall, rigid tubes. By utilizing one or more mandrel-like extensions of varying diameters and different punches, a tube may be formed with uniform wall thicknesses, but with thickened wall sections at selected portions thereof. Examples of this system for forming hollow tubes are illustrated in my U.S. Pat. Nos. 4,002,286 issued Jan. 11, 1977; 4,277,969 issued Jul. 14, 1981; 4,292,831 issued Oct. 6, 1981; 4,435,972 issued Mar. 13, 1984 and 4,991,421 issued Feb. 12, 1991. These patents illustrate methods for forming hollow tubes for various purposes with pre-selected wall thicknesses.
Thus, the invention herein relates to a method for forming a hollow, extruded metal axle shaft upon whose end a pre-formed metal flange is fastened for inexpensively fabricating a lightweight shaft with adequate strength and rigidity for its required purpose.